1. Field of the Invention
The present invention relates to hydraulic couplings used in undersea drilling and production applications and seals used in those couplings. More particularly, the invention involves a four-piece coupling and a reusable metal seal for sealing the junction between the male and female members of the coupling.
2. Related Art
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male and a female member with soft seals positioned within the female member to seal the junction between the male and female members.
The female member is generally a cylindrical body with a relatively large diameter longitudinal bore at one end and a relatively small diameter longitudinal bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore contains the soft seals and receives the male portion of the coupling. The male member includes a cylindrical portion at one end having a diameter approximately equal to the diameter of the large bore in the female portion of the coupling. The male member also includes a connection at its other end to facilitate connection to hydraulic lines. When the cylindrical portion of the male member is inserted into the large bore of the female member, according to the various embodiments of the device, the soft seals, resembling O-rings, either abut the end, or face, of the male member or engage the male member about its circumference. The hydraulic fluid is then free to flow through the female and male portions of the coupling, and the seals prevent that flow from escaping about the joint in the coupling.
In some instances a check valve may be installed in the female member and also in the male member. Each check valve is open when the coupling is made up; however, each check valve closes when the coupling is broken, so as to prevent fluid from leaking out the system of which the coupling is a part.
The soft seals have numerous disadvantages, the principal ones being (1) the inability of the seal to withstand the deteriorating effects of the subsea environment for extended periods of time, and (2) the inability of the soft seal to contain the higher pressures being imposed on the hydraulic systems.
A metal seal is available which better withstands both the deteriorating effects of the environment and the higher pressures. That seal is a crush-type which is positioned between the end of the male portion of the coupling and the internal end of the large bore in the female portion. When the male portion is inserted into the female, the metal seal is crushed between the two portions and a seal is effectuated between the two. In view of the crushing action, the seal can be used only once. If the coupling is separated for any reason, the once-used crushed seal must be replaced with a new seal.
The male and female portions of the above couplings are each one-piece devices; and the seal is placed either in a circumferential groove about the interior of the large bore in the female member, or it rests at the interior end of that bore for engagement with the end of the male portion. Particularly in the case of the latter face-type seals, there is no mechanism for retention of the seal in the female section. If the coupling is parted under pressure, the seal will generally blow out of the female section and be lost. There may also be risk of injury to the operator parting the coupling.